UNITED NATIONS (AP) _ The Security Council voted Friday to scale down the U.N. peacekeeping force in Croatia and deploy troops on the country's borders.

But the mandate is vague and does not address crucial issues such as the number of troops to be deployed and their exact mission.

The council unanimously agreed to split the U.N. force in Yugoslavia into three parts: a reduced force in Croatia and missions in Bosnia and Macedonia that will remain essentially unchanged.

The mandate comes after Croatia gave in to Western pressure and dropped its threat to expel the 12,000 U.N. peacekeepers stationed in Croatia after their mandate expired Friday.

Withdrawing the peacekeepers would have been ``an invitation to a new round of intense violence that ... would leave thousands more dead,'' said U.S. Deputy Ambassador Karl Inderfurth.

But he cautioned that negotiations will be difficult and ``whether we have bought more than time for Bosnia and Croatia, we cannot now determine.''

Croatia has demanded that the U.N. soldiers take control of the borders and halt arms shipments to Croatian Serb rebels from their ethnic brethren in Bosnia and Serbia. The Croatian Serbs have opposed any change in the mission.

The new force in Croatia will be called the United Nations Confidence Restoration Operation in Croatia. Croatia had demanded that its name be in the title so as to imply recognition of Croatian sovereignty over all its territory, including the one-third held by rebel Serbs.

Croatian Serb leader Milan Martic opposed any change to the U.N. mandate or its name, saying in a letter to U.N. Secretary-General Boutros Boutros-Ghali that the new name ``signifies an essential change in the mandate.''

Martic warned against disregarding Croatian Serb demands, saying: ``It is needless to warn you how greatly peace in the region could be affected in such an event.''

The new mandate defines the peacekeepers' role in Croatia as monitoring and controlling ``military personnel, equipment supplies and weapons'' that cross the border. It does not authorize peacekeepers to use force to stop shipments or say whether they will have fixed posts or mobile patrols.

About 1,000 peacekeepers are expected to be posted on the border as part of a total force of 7,000 to 8,000 troops, according to U.S. officials.

The mandate says the force is an ``interim arrangement to create the conditions that will facilitate a negotiated settlement.''

``A peaceful settlement in Croatia is only possible if this ... is strictly implemented,'' Croatian Ambassador Mario Nobilo said.

The resolution calls on Boutros-Ghali to report to the council by April 21 on implementing the mandate.

In his speech to the council, Nobilo warned that Croatia considers itself to have ``an exclusive right of veto in the upcoming negotiations.''

In its earlier threat to expel peacekeepers, Croatia said their presence only cemented rebel Serb control over parts of the country. A 1991 war between Croatian forces and rebel Serbs left about 10,000 people dead.

There are about 22,000 peacekeepers in Bosnia and about 1,000 U.N. troops in Macedonia.

The new mission in Macedonia is called the United Nations Preventive Deployment Force, the resolution says, and the mission in Bosnia retains its current name, the U.N. Protection Force.